I just finished a short animated film. I've rendered it to .mov files. Each time it's getting this strange white bar at the bottom of the video. Looks to be a pixel high and runs the horizontal length of the image.
I'm working at 2.39:1 ratio (rendering at 1920x803). I'm using a black background in After Effects and all of my footage is sized to extend past the live area.
I've rendered with and without letterbox bars. Without the bars, the line rests at the bottom of the image. With bars it rests at the bottom of the bars.
Most CODECs encode with a strict requirement that the screen aspect ratio is divisible by 4x4 blocks - or something similar. I believe having an odd numbered height forces the encoder to insert a line. Try setting your comp to either 802 or 804 and see if this fixes your issue.